Pathogenetic mechanisms in thyroid follicular-cell neoplasia

Molecular Profiling of Papillary Thyroid Carcinoma in Korea with a High Prevalence of BRAFV600E Mutation

BACKGROUND

The BRAF^V600E mutation in papillary thyroid carcinoma (PTC) is particularly prevalent in Korea, and a considerable number of wild-type BRAF PTCs harbor RAS mutations. In addition, subsets of other genetic alterations clearly exist, but their prevalence in the Korean population has not been well studied. Recent increased insight into noninvasive encapsulated follicular variant PTC has prompted endocrine pathologists to reclassify this entity as "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP). This study analyzed the genetic alterations among the histologic variants of PTC, including NIFTP.

METHODS

Mutations of the BRAF and RAS genes and rearrangement of the RET/PTC1, NTRK1, and ALK genes using 769 preoperative fine-needle aspiration specimens and resected PTCs were analyzed.

RESULTS

Molecular alterations were found in 687 (89.3%) of 769 PTCs. BRAF^V600E mutation (80.8%) was the most frequent alteration, followed by RAS mutation and RET/PTC1, NTRK1, and ALK rearrangements (5.6%, 2.1%, 0.4%, and 0%, respectively). The low prevalence of NTRK1 fusions and the absence of an ALK fusion detected in Korea may also be attributed to the higher prevalence of the BRAF^V600E mutation. There were significant differences in the frequency of the genetic alterations among the histologic variants of PTC. The prevalence of NIFTP in PTC was 2.7%, and among the NIFTPs, 28.6% and 57.1% harbored BRAF and RAS mutations, respectively. Clinicopathologic factors and mutational profiles between NIFTP and encapsulated follicular variant PTC with capsular invasion group were not significantly different.

CONCLUSIONS

Genetic alterations in PTC vary among its different histologic variants and seem to be different in each ethnic group.

Frequent BRAF V600E and Absence of TERT Promoter Mutations Characterize Sporadic Pediatric Papillary Thyroid Carcinomas in Japan

Pediatric papillary thyroid carcinoma (PTC) has unique features but requires further genetic investigation. Moreover, there has been increasing concern about the risk for pediatric PTC in Japan after the Fukushima accident. This study aims to evaluate the frequencies of BRAF and TERT promoter mutations and to examine their significance in non-radiation-associated pediatric PTCs in Japan. We enrolled 81 pediatric PTC patients aged ≤20 years. The control group included 91 adult PTCs from patients >20 years old. BRAF and TERT mutations were analyzed by allele-specific-PCR and/or Sanger sequencing. Compared with adult PTCs, pediatric PTCs exhibited larger tumor size, more frequent lymph node metastasis, and less classical histology. The prevalence of BRAF ^V600E in pediatric PTCs was 54% and significantly lower than that in adults of 85%. In the pediatric PTCs, BRAF ^V600E was positively associated with older age, classical histology, and the lymph node metastasis but independent from other clinicopathological factors. TERT mutations were identified in 13% of adults and in none of the pediatric PTCs. In conclusion, pediatric PTCs are characterized by more advanced clinicopathological features, lower BRAF ^V600E frequency, and absence of TERT mutation. The BRAF ^V600E frequency in this study is similar to the reported BRAF ^V600E frequency in the ultrasonographically screened pediatric PTCs in Fukushima.

Atypical adenoma of the thyroid diagnosed as anaplastic cancer by cytopathology

Atypical adenoma of the thyroid is a rare form of tumor, and its accurate diagnosis prior to surgical resection is difficult as the histological and pathological morphologies are very similar to those of anaplastic thyroid carcinoma (ATC), and its anaplastic transformation remains to be elucidated. We reported a case of a 75-year-old female with a thyroid isthmus nodule diagnosed repeatedly by FNAC as anaplastic carcinoma. Both the first and second FNAC specimen slides showed a large number of scattered or aggregated atypical cells consisting of large, pleomorphic nuclei with irregular membranes, chromatin clumps and prominent nucleoli. The morphology of the surgical specimen was similar to that of an anaplastic carcinoma and although it showed signs of transition from a normal follicular epithelium, there was no invasive growth or mitosis. This lesion was diagnosed as an atypical adenoma, and a papillary carcinoma was also present in the right lobe of the thyroid. Here we evaluate the molecular features of atypical adenomas in comparison with 9 ATC samples, and discuss whether or not atypical adenomas represent a form of premalignant lesion. Ki-67 expression was found to be very low in atypical adenomas whereas all ATC samples showed high levels of Ki-67 expression. Epithelial-mesenchymal transition (EMT) marker expression suggested that atypical adenomas maintain their epithelial phenotype to a higher degree than do ATCs. Differential diagnosis between ATC and atypical adenoma is difficult by cytological and histological methods alone, and Ki-67 and EMT marker expression may support the diagnosis.

NADPH Oxidase NOX4 Is a Critical Mediator of BRAFV600E-Induced Downregulation of the Sodium/Iodide Symporter in Papillary Thyroid Carcinomas

AIMS

The BRAF^V600E oncogene, reported in 40%-60% of papillary thyroid cancer (PTC), has an important role in the pathogenesis of PTC. It is associated with the loss of thyroid iodide-metabolizing genes, such as sodium/iodide symporter (NIS), and therefore with radioiodine refractoriness. Inhibition of mitogen-activated protein kinase (MAPK) pathway, constitutively activated by BRAF^V600E, is not always efficient in resistant tumors suggesting that other compensatory mechanisms contribute to a BRAF^V600E adaptive resistance. Recent studies pointed to a key role of transforming growth factor β (TGF-β) in BRAF^V600E-induced effects. The reactive oxygen species (ROS)-generating NADPH oxidase NOX4, which is increased in PTC, has been identified as a new key effector of TGF-β in cancer, suggestive of a potential role in BRAF^V600E-induced thyroid tumors.

RESULTS

Here, using two human BRAF^V600E-mutated thyroid cell lines and a rat thyroid cell line expressing BRAF^V600E in a conditional manner, we show that NOX4 upregulation is controlled at the transcriptional level by the oncogene via the TGF-β/Smad3 signaling pathway. Importantly, treatment of cells with NOX4-targeted siRNA downregulates BRAF^V600E-induced NIS repression. Innovation and Conclusion: Our results establish a link between BRAF^V600E and NOX4, which is confirmed by a comparative analysis of NOX4 expression in human (TCGA) and mouse thyroid cancers. Remarkably, analysis of human and murine BRAF^V600E-mutated thyroid tumors highlights that the level of NOX4 expression is inversely correlated to thyroid differentiation suggesting that other genes involved in thyroid differentiation in addition to NIS might be silenced by a mechanism controlled by NOX4-derived ROS. This study opens a new opportunity to optimize thyroid cancer therapy. Antioxid. Redox Signal. 26, 864-877.

Integrated data analysis reveals potential drivers and pathways disrupted by DNA methylation in papillary thyroid carcinomas

BACKGROUND

Papillary thyroid carcinoma (PTC) is a common endocrine neoplasm with a recent increase in incidence in many countries. Although PTC has been explored by gene expression and DNA methylation studies, the regulatory mechanisms of the methylation on the gene expression was poorly clarified. In this study, DNA methylation profile (Illumina HumanMethylation 450K) of 41 PTC paired with non-neoplastic adjacent tissues (NT) was carried out to identify and contribute to the elucidation of the role of novel genic and intergenic regions beyond those described in the promoter and CpG islands (CGI). An integrative and cross-validation analysis were performed aiming to identify molecular drivers and pathways that are PTC-related.

RESULTS

The comparisons between PTC and NT revealed 4995 methylated probes (88% hypomethylated in PTC) and 1446 differentially expressed transcripts cross-validated by the The Cancer Genome Atlas data. The majority of these probes was found in non-promoters regions, distant from CGI and enriched by enhancers. The integrative analysis between gene expression and DNA methylation revealed 185 and 38 genes (mainly in the promoter and body regions, respectively) with negative and positive correlation, respectively. Genes showing negative correlation underlined FGF and retinoic acid signaling as critical canonical pathways disrupted by DNA methylation in PTC. BRAF mutation was detected in 68% (28 of 41) of the tumors, which presented a higher level of demethylation (95% hypomethylated probes) compared with BRAF wild-type tumors. A similar integrative analysis uncovered 40 of 254 differentially expressed genes, which are potentially regulated by DNA methylation in BRAFV600E-positive tumors. The methylation and expression pattern of six selected genes (ERBB3, FGF1, FGFR2, GABRB2, HMGA2, and RDH5) were confirmed as altered by pyrosequencing and RT-qPCR.

CONCLUSIONS

DNA methylation loss in non-promoter, poor CGI and enhancer-enriched regions was a significant event in PTC, especially in tumors harboring BRAFV600E. In addition to the promoter region, gene body and 3'UTR methylation have also the potential to influence the gene expression levels (both, repressing and inducing). The integrative analysis revealed genes potentially regulated by DNA methylation pointing out potential drivers and biomarkers related to PTC development.

Molecular Pathology of Anaplastic Thyroid Carcinomas: A Retrospective Study of 144 Cases

BACKGROUND

Anaplastic thyroid carcinoma (ATC) is a rare tumor, with poorly defined oncogenic molecular mechanisms and limited therapeutic options contributing to its poor prognosis. The aims of this retrospective study were to determine the frequency of anaplastic lymphoma kinase (ALK) translocations and to identify the mutational profile of ATC including TERT promoter mutations.

METHODS AND MATERIALS

One hundred and forty-four ATC cases were collected from 10 centers that are a part of the national French network for management of refractory thyroid tumors. Fluorescence in situ hybridization analysis for ALK rearrangement was performed on tissue microarrays. A panel of 50 genes using next-generation sequencing and TERT promoter mutations using Sanger sequencing were also screened.

RESULTS

Fluorescence in situ hybridization was interpretable for 90 (62.5%) cases. One (1.1%) case was positive for an ALK rearrangement with a borderline threshold (15% positive cells). Next-generation sequencing results were interpretable for 94 (65.3%) cases, and Sanger sequencing (TERT) for 98 (68.1%) cases. A total of 210 mutations (intronic and exonic) were identified. TP53 alterations were the most frequent (54.4%). Forty-three percent harbored a mutation in the (H-K-N)RAS genes, 13.8% a mutation in the BRAF gene (essentially p.V600E), 17% a PI3K-AKT pathway mutation, 6.4% both RAS and PI3K pathway mutations, and 4.3% both TP53 and PTEN mutations. Nearly 10% of the cases showed no mutations of the RAS, PI3K-AKT pathways, or TP53, with mutations of ALK, ATM, APC, CDKN2A, ERBB2, RET, or SMAD4, including mutations not yet described in thyroid tumors. Genes encoding potentially druggable targets included: mutations in the ATM gene in four (4.3%) cases, in ERBB2 in one (1.1%) case, in MET in one (1.1%) case, and in ALK in one (1.1%) case. A TERT promoter alteration was found in 53 (54.0%) cases, including 43 C228T and 10 C250T mutations. Three out of our cases did not harbor mutations in the panel of genes with therapeutic interest.

CONCLUSION

This study confirms that ALK rearrangements in ATC are rare and that the mutational landscape of ATC is heterogeneous, with many genes implicated in the follicular epithelial cell dedifferentiation process. This may explain the limited effectiveness of targeted therapeutic options tested so far.

Prognostic significance of diffuse sclerosing variant papillary thyroid carcinoma: a systematic review and meta-analysis

OBJECTIVE

Diffuse sclerosing variant papillary thyroid carcinoma (DSVPTC) is an uncommon variant of papillary thyroid carcinoma (PTC). The biological behaviors and prognostic outcomes of this variant, however, are still controversial. The aim of this systematic review and meta-analysis is to investigate the prognostic significance and outcomes of DSVPTCs in comparison with classical PTCs (cPTCs).

METHODS

An electronic search was performed in five libraries: PubMed, Scopus, ISI, World Health Organization Global Health Library (WHO GHL) and Virtual Health Library (VHL) in June 2016. Published data were extracted and were pooled into odds ratios (OR), mean differences and corresponding 95% confidence intervals (CI) using random-effect model. Publication bias was analyzed using Egger's regression test and funnel plot observation.

RESULTS

From 315 articles, we included 16 articles comprising 732 DSVPTCs for meta-analysis. Overall, DSVPTC manifested more aggressive clinicopathological behaviors than cPTC such as higher rate of vascular invasion (OR: 5.33; 95% CI: 3.08-9.23), extrathyroidal extension (OR: 2.96; 95% CI: 2.04-4.30), lymph node metastasis (OR: 5.40; 95% CI: 2.82-10.35), distant metastasis (OR: 3.61; 95% CI: 1.89-6.88) and were more likely to relapse (OR: 2.83; 95% CI: 1.59-5.05). DSVPTC patients were associated with a worsened overall survival (HR: 1.89; 95% CI: 1.36-2.62).

CONCLUSION

DSVPTCs should be considered high-risk PTCs because of high propensity for tumor invasion, metastasis, relapse and mortality. Aggressiveness of DSVPTCs might be related to a different molecular pathway than that in cPTCs.

Natural history of thyroid cancer [Review]

Thyroid cancers have long been considered to arise in middle age and, after their repeated proliferation, resulting in further damage to the genome, they progress to more aggressive and lethal cancers. However, in 2014, some studies were reported that might lead to a marked change in our understanding of the natural history of thyroid cancer. A high prevalence of papillary carcinoma in the young suggested that the first initiation of thyroid cancer is likely to occur in the infantile period. Such a conclusion was also supported by a very slow growth rate of papillary microcarcinomas (PMCs) in an observation trial. The proliferation rate of PMCs was negatively correlated with the age, and surgery to remove PMCs did not contribute to reduce mortality from thyroid cancer. These findings strongly suggested the existence of self-limiting cancers, which are truly malignant but do not progress to lethal cancers, for the first time in human history. The early detection of self-limiting cancers results in overdiagnosis. Ultrasonographic screening of the thyroid in the young should be avoided. Lethal thyroid cancers, whose origin is still unknown, appear suddenly after middle age. In the elderly, thyroid cancers are a mixture of self-limiting and lethal cancers; thus, when thyroid cancer is detected, careful follow-up with examination of its growth rate is required.

Relationships of BRAF mutation and HMGB1 to papillary thyroid carcinoma

A poor papillary thyroid cancer (PTC) prognosis is strongly associated with the BRAF V600E mutation. During tumor progression, levels of the high mobility group box 1 (HMGB1) protein are often dysregulated. Results herein demonstrate that HMGB1 protein levels differ between tumor and adjacent non-tumor tissue and that HMGB1 mRNA levels were higher in wild-type BRAF PTC tissues than in BRAF V600E PTC tissues (2-△Ct 0.31 ± 0.25 vs. 0.16 ± 0.12; P < 0.05). HMGB1 protein levels also differed in the same manner (wild-type BRAF PTC tissues 0.11 ± 0.04 vs. BRAF V600E PTC tissues 0.03 ± 0.03; P < 0.001). Although not detected in peripheral blood, low levels of HMGB1 were significantly related to PTC cell lymph node metastasis and extra-glandular infiltration (P = 0.045 and P = 0.002). Experimental results at the cellular level were consistent with tissues and further verified the relationship of BRAF V600E and HMGB1. These findings demonstrate that the BRAF V600E mutation down-regulates levels of HMGB1, likely through activation of the mitogen-activated protein kinase (MAPK) signaling pathways.

A genome-wide association study yields five novel thyroid cancer risk loci

The great majority of thyroid cancers are of the non-medullary type. Here we report findings from a genome-wide association study of non-medullary thyroid cancer, including in total 3,001 patients and 287,550 controls from five study groups of European descent. Our results yield five novel loci (all with Pcombined<3 × 10-8): 1q42.2 (rs12129938 in PCNXL2), 3q26.2 (rs6793295 a missense mutation in LRCC34 near TERC), 5q22.1 (rs73227498 between NREP and EPB41L4A), 10q24.33 (rs7902587 near OBFC1), and two independently associated variants at 15q22.33 (rs2289261 and rs56062135; both in SMAD3). We also confirm recently published association results from a Chinese study of a variant on 5p15.33 (rs2736100 near the TERT gene) and present a stronger association result for a moderately correlated variant (rs10069690; OR=1.20, P=3.2 × 10-7) based on our study of individuals of European ancestry. In combination, these results raise several opportunities for future studies of the pathogenesis of thyroid cancer.

The changing characteristics and molecular profiles of papillary thyroid carcinoma over time: a systematic review

BACKGROUND

The genetic alterations of papillary thyroid carcinoma (PTC) have been reported to change over the past few decades. We performed this systematic review to further examine the trends and modifications of patient demographic, clinicopathological features and molecular profiles of PTC over time.

METHODS

A literature search was performed within six electronic databases to identify relevant articles. The inclusion criteria were published studies investigating BRAF mutations, RET/PTC rearrangements or RAS mutations in PTCs or classical PTCs. Two teams of reviewers independently screened titles and abstracts of all articles. Full texts of potential articles were read and extracted data were listed and stratified into an excel file according to country, city, institution, and surgical time period. Student t test and Pearson Chi-square were used to analyze the trends of demographic and clinicopathological features of PTC patients and the prevalence of each genetic alteration in individual institutions.

RESULTS

From 3139 articles, we included 16 articles for final analysis. Our results showed an increasing trend of BRAF and a decreasing trend of RET/PTC prevalence over time in PTCs and classical PTCs, accompanied by an older age of PTC patients, an increase in proportion of PTMC and less aggressive behaviours of tumours.

CONCLUSIONS

The demographic and clinicopathological characteristics and molecular profile of PTCs have been changing over the past few decades. These modifications suggest changes in etiologies and risk factors of thyroid cancer that influence the tumorigenesis of PTCs.

Papillary thyroid carcinoma with nodular fasciitis-like stroma and β-catenin mutations should be renamed papillary thyroid carcinoma with desmoid-type fibromatosis

Various histological variants of papillary thyroid carcinoma have been reported, some with clinical implications, some with peculiar, sometimes misleading morphologies. One of these rare and poorly characterized variants is papillary thyroid carcinoma with nodular fasciitis-like stroma, of which fewer than 30 cases have been documented, mostly as isolated reports. It is a dual tumor comprising a malignant epithelial proliferation that harbors typical features of conventional papillary thyroid carcinoma, admixed with a prominent mesenchymal proliferation resembling nodular fasciitis or fibromatosis. Thus, the terms papillary thyroid carcinoma with nodular fasciitis-like stroma and papillary thyroid carcinoma with fibromatosis-like stroma are used interchangeably; however, the former term suggests a self-limited and regressing disease, whereas the latter one suggests a recurrent and potentially aggressive one. Better genetic and ultrastructural characterization could lead to more appropriate terminology and management. We performed detailed clinicopathological and molecular analyses of two cases of PTC with prominent mesenchymal proliferation that developed in the thyroid gland of two male patients aged 34 and 48. In both cases, the epithelial component harbored a heterozygous somatic activating BRAF mutation (p.V600E). Also, in both cases, the mesenchymal component showed typical aberrant nuclear and cytoplasmic immunoreactivity for β-catenin and harbored a heterozygous somatic activating mutation in the corresponding CTNNB1 gene (p.S45P). This mutation has never been reported in thyroid stroma; in other tissues, it is typical of desmoid-type fibromatosis rather than nodular fasciitis-like stroma. We therefore propose that in cases of papillary thyroid carcinoma with a prominent mesenchymal component, mutations in CTNNB1 should be sought; when they are present, the term 'papillary thyroid carcinoma with desmoid-type fibromatosis' should be used. As the mesenchymal component of these tumors is not expected to concentrate radioactive iodine, special considerations apply to clinical evaluation and follow-up, which should be brought to the attention of the treating specialist.

Nodular thyroid disease in the elderly: novel molecular approaches for the diagnosis of malignancy

Epithelial thyroid cancers (TC) comprise two differentiated histotypes (DTC), the papillary (PTC) and the follicular (FTC) thyroid carcinomas which, following dedifferentiation, are assumed to give rise to the poorly differentiated thyroid carcinomas and the rare, but highly aggressive and invariably fatal, anaplastic thyroid carcinomas. Although thyroid cancer mortality has not been changed, its annual incidence has increased over the last two decades, mainly because of the improved ability to diagnose malignant transformation in small non-palpable thyroid nodules. Despite DTC patients have a favorable prognosis, aggressive disease is more frequently observed in the elderly showing a higher disease-specific mortality. Of relevance is the high prevalence of nodular thyroid disease in aged patients being higher than 90%, in women older than 60 year, and 60% in men older than 80 year. This implies a careful evaluation of thyroid nodules in this group of patients in order to exclude malignancy. In fact, despite the tremendous progress in the comprehension of the underlying molecular mechanisms deregulated in DTC progression, several aspects of their clinical management remain to be solved and novel diagnostic strategies are sorely needed. Here, we will attempt to review new molecular approaches, which are currently being exploited in order to ameliorate the diagnosis of thyroid nodules.

Molecular Programs Underlying Asymmetric Stem Cell Division and Their Disruption in Malignancy

Asymmetric division of stem cells is a highly conserved and tightly regulated process by which a single stem cell produces two unequal daughter cells. One retains its stem cell identity while the other becomes specialized through a differentiation program and loses stem cell properties. Coordinating these events requires control over numerous intra- and extracellular biological processes and signaling networks. In the initial stages, critical events include the compartmentalization of fate determining proteins within the mother cell and their subsequent passage to the appropriate daughter cell in order to direct their destiny. Disturbance of these events results in an altered dynamic of self-renewing and differentiation within the cell population, which is highly relevant to the growth and progression of cancer. Other critical events include proper asymmetric spindle assembly, extrinsic regulation through micro-environmental cues, and non-canonical signaling networks that impact cell division and fate determination. In this review, we discuss mechanisms that maintain the delicate balance of asymmetric cell division in normal tissues and describe the current understanding how some of these mechanisms are deregulated in cancer.

Expression of MicroRNAs in Thyroid Carcinoma

MicroRNA (miRNA) are negative regulators of gene expression and subsequent protein production. This method of action translates into regulatory control over cellular processes, including development, signaling, metabolism, and apoptosis. A broad range of miRNA are shown to have abnormal expressions in thyroid cancers which could explain the pathology of tumor oncogenesis and disease progression. A review is conducted of the current research on miRNA dysregulation in thyroid cancers, including papillary thyroid carcinoma (PTC), follicular thyroid carcinoma (FTC), anaplastic thyroid cancer (ATC), and medullary thyroid carcinoma (MTC). Dysregulated miRNA and their associated regulatory pathways are identified and their oncogenic and pathological significance are discussed.

Sonic Hedgehog Signaling in Thyroid Cancer

Thyroid cancer is the most common malignancy of the endocrine system. The initiation of thyroid cancer is often triggered by a genetic mutation in the phosphortidylinositol-3 kinase (PI3K) or mitogen-activated protein kinase (MAPK) pathway, such as RAS and BRAF, or by the rearrangement of growth factor receptor tyrosine kinase genes such as RET/PTC. The sonic hedgehog (Shh) pathway is evolutionarily conserved and plays an important role in the embryonic development of normal tissues and organs. Gene mutations in the Shh pathway are involved in basal cell carcinomas (BCC). Activation of the Shh pathway due to overexpression of the genes encoding the components of this pathway stimulates the growth and spread of a wide range of cancer types. The Shh pathway also plays an important role in cancer stem cell (CSC) self-renewal. GDC-0449 and LDE-225, two inhibitors of this pathway, have been approved for treating BCC and are being tested as a single agent or in combination with other drugs for treating various other cancers. Here, we review the recent findings on activation of the Shh pathway in thyroid cancer and its role in maintaining thyroid CSC self-renewal. We also summarize the recent developments on crosstalk of the Shh pathway with the MAPK and PI3K oncogenic pathways, and its implications for combination therapy.

RAS Mutations, and RET/PTC and PAX8/PPAR-gamma Chromosomal Rearrangements Are Also Prevalent in Benign Thyroid Lesions: Implications Thereof and A Systematic Review

BACKGROUND

Molecular markers associated with thyroid malignancy are increasingly being used as differential diagnostic tools for thyroid nodules. However, little has been reported recently regarding the prevalence of these markers in benign lesions. The literature was systematically reviewed to examine studies that reported on the prevalence of these markers in benign thyroid lesions.

METHODS

Appropriate studies published between January 1, 2000, and April 30, 2015, and cataloged in PubMed, Embase, Cochrane, Scopus, and Web of Science databases were searched for by combining different keywords for "thyroid tumor" with both general and specific keywords for "molecular marker" by using "AND" as the Boolean operator. All studies meeting criteria that reported the prevalence of RAS mutations, and RET/PTC and PAX8/PPAR-gamma chromosomal rearrangements in benign thyroid lesions were included for study.

RESULTS

A total of 64 articles (including 8162 patients, of whom 42.5% had benign lesions) that met all the study criteria were systematically reviewed and abstracted. Among 35 studies examining RAS mutations, the reported prevalence of RAS mutation in benign lesions ranged from 0% to 48%. In 38 studies examining RET/PTC rearrangements, the prevalence in benign lesions ranged from 0% to 68%. PAX8/PPAR-gamma rearrangements were examined in 27 studies, with the prevalence in benign lesions ranging from 0% to 55%.

CONCLUSION

The presence of these biomarkers and the tremendous variation in reports of their prevalence in benign lesions suggests the need for caution when including these markers in diagnostic decisions. Further understanding of the importance of these markers, as well as newly discovered markers of thyroid malignancy, may be required in order to avoid overtreatment of patients with benign thyroid tumors.

Comprehensive analysis of long noncoding RNA–mRNA co-expression patterns in thyroid cancer

Novel molecular-targeted treatments show great prospects for radioiodine-refractory and surgically inoperable thyroid carcinomas.

EphB3 Stimulates Cell Migration and Metastasis in a Kinase-dependent Manner through Vav2-Rho GTPase Axis in Papillary Thyroid Cancer

Eph receptors, the largest subfamily of transmembrane tyrosine kinase receptors, have been increasingly implicated in various physiologic and pathologic processes, and the roles of the Eph family members during tumorigenesis have recently attracted growing attentions. In the present study, we explored the function of EphB3, one member of Eph family, in papillary thyroid cancer (PTC). We found that the expression of EphB3 was significantly elevated in PTC. Either overexpression of EphB3 or activation of EphB3 by EfnB1-Fc/EfnB2-Fc stimulated in vitro migration of PTC cells. In contrast, siRNA-mediated knockdown of EphB3 or EphB3-Fc treatment, which only blocked EphB3-mediated forward signaling, inhibited migration and metastasis of PTC cells. A mechanism study revealed that EphB3 knockdown led to suppressed activity of Rac1 and enhanced activity of RhoA. Moreover, we found that Vav2, an important regulator of Rho family GTPases, was activated by EphB3 in a kinase-dependent manner. Altogether, our work suggested that EphB3 acted as a tumor promoter in PTC by increasing the in vitro migration as well as the in vivo metastasis of PTC cells through regulating the activities of Vav2 and Rho GTPases in a kinase-dependent manner.

Does Molecular Genotype Provide Useful Information in the Management of Radioiodine Refractory Thyroid Cancers? Results of a Retrospective Study

INTRODUCTION

Whether mutation status should be used to guide therapy is an important issue in many cancers. We correlated mutation profile in radioiodine-refractory (RAIR) metastatic thyroid cancers (TCs) with patient outcome and response to tyrosine kinase inhibitors (TKIs), and discussed the results with other published data.

MATERIALS AND METHODS

Outcome in 82 consecutive patients with metastatic RAIR thyroid carcinoma prospectively tested for BRAF, RAS and PI3KCA mutations was retrospectively analyzed, including 55 patients treated with multikinase inhibitors.

RESULTS

Papillary thyroid carcinomas (PTCs) were the most frequent histological subtype (54.9 %), followed by poorly differentiated thyroid carcinoma [PDTC] (30.5 %) and follicular thyroid carcinoma [FTC] (14.6 %). A genetic mutation was identified in 23 patients (28 %) and BRAF was the most frequently mutated gene (23 %). Median progression-free survival (PFS) on first-line TKI treatment was 14.6 months (95% CI 9.9-18.4). BRAF mutation positively influenced median PFS, both in the entire TKI-treated cohort (median PFS 34.7 months versus 11.6 months; hazard ratio [HR] 0.29; 95% CI 0.09-0.98; p = 0.03) and in the TKI-treated PTC cohort (n = 22) [log-rank p = 0.086; HR 2.95; 95 % CI 0.81-10.70). However, in TKI-treated patients, PDTC histologic subtype was the only independent prognostic factor for PFS identified in the multivariate analysis (HR 2.36; 95% CI 1.01-5.54; p = 0.048).

CONCLUSION

Patients with BRAF-mutant PTC had a significantly longer PFS than BRAF wild-type when treated with TKIs. However, due to the small number of BRAF-mutant patients, further investigations are required, especially to understand the potential positive effect of BRAF mutations in RAIR TC patients while having a negative prognostic impact in RAI-sensitive PTC patients.

Crohn's Disease Is Associated with the Risk for Thyroid Cancer

BACKGROUND

It is known that inflammatory bowel disease (IBD) is associated with a high risk for some of extraintestinal cancers. The aim of this study was to identify whether IBD is associated with thyroid cancer using a large national database.

METHODS

We performed a case-control study using the 2012 National Inpatient Sample (NIS) database. The study group included all patients with Crohn's disease (CD) (ICD-9 Code: 555) and ulcerative colitis (UC) (ICD-9 Code: 556), and the control group included all patients with diverticulitis (ICD-9 Code: 562.11, 562.13). Both univariable and multivariable analyses were performed to assess the risk factors associated with thyroid cancer.

RESULTS

We analyzed more than 28 million hospitalizations in 2012, with 289,935 being IBD-related admissions and 315,145 being diverticulitis-related admissions. Subjects who had IBD were found to be significantly more likely to have thyroid cancer than those with diverticulitis (odds ratio = 1.97 [1.5-2.6], P = 0.033). There was no difference between men and women in the prevalence of thyroid cancer in IBD (P = 0.6). There was no difference between CD and UC (P = 0.14) and between UC and diverticulitis (P = 0.93). In multivariate analysis, CD was found to be associated with thyroid cancer (odds ratio = 2.3 [1.06-5.1], P = 0.034). Age was shown to be a protective factor in the presence of thyroid cancer (P < 0.005), and a higher Charlson comorbidity index was associated with the presence of thyroid cancer (odds ratio, 1.5 [1.3-1.7]; P < 0.001).

CONCLUSIONS

Our study showed that CD, not UC, is associated with a higher risk for thyroid cancer. It is recommended that patients with CD may need a close monitoring of thyroid diseases.

Identification of Specific Long Non-Coding RNA Expression: Profile and Analysis of Association with Clinicopathologic Characteristics and BRAF Mutation in Papillary Thyroid Cancer

BACKGROUND

In recent years, long non-coding RNAs (lncRNAs) have been shown to play a critical regulatory role in cancer biology. However, the contribution of lncRNAs to papillary thyroid cancer (PTC) remains largely unknown.

METHODS

RNA sequencing and quantitative reverse transcription polymerase chain reaction were used to detect and verify changes to the transcriptome profile in 12 PTC tissues compared to paired normal adjacent tissues. The statistical correlation between differentially expressed lncRNAs and clinicopathologic characteristics was analyzed, and potential lncRNA functions were predicted by examining annotations for the co-expressed mRNAs. Furthermore, the specific subgroup patterns of the PTC transcriptome remodeled by BRAF mutations were also analyzed.

RESULTS

A total of 188 lncRNAs and 505 mRNAs were differentially expressed in 50% or more of the PTC tissues (fold change >2; p < 0.05) as assessed by RNA-sequencing compared with paired normal adjacent tissues. Forty-seven lncRNAs and 39 mRNAs were verified in 31 pairs of PTC specimens using quantitative reverse transcription polymerase chain reaction, and the results were consistent with the RNA sequencing data. The lncRNAs NONHSAT076747 and NONHSAT122730 were associated with lymph node metastasis, and NONHSAG051968 expression was negatively correlated with tumor size. A co-expression network between differentially expressed lncRNAs and protein-coding RNAs was constructed and analyzed, and functional analysis suggested that the differentially expressed genes mainly participate in ECM-receptor interactions and the focal adhesion pathway. Furthermore, a specific PTC transcriptome subtype pattern stratified by BRAF mutation was also uncovered. The p53 signaling pathway was the most highly enriched pathway among the BRAF mutation-related genes.

CONCLUSIONS

This study reveals specific changes to the lncRNA profile associated with PTC, and provides new insight into its pathogenesis. The PTC-associated lncRNAs NONHSAG051968, NONHSAT076747, and NONHSAT122730 might be potential diagnostic and therapeutic targets for PTC patients, and lncRNAs with subtype-specific expression stratified by BRAF mutation might be significant in individual molecular subtypes.

Thyroid-stimulating hormone improves insulin sensitivity in skeletal muscle cells via cAMP/PKA/CREB pathway-dependent upregulation of insulin receptor substrate-1 expression

Thyroid-stimulating hormone (TSH) receptor is expressed in extrathyroidal tissues such as hepatocytes, adipocytes, and skeletal muscle, which suggests a possible novel role of TSH in various metabolic processes in extrathyroidal tissues independent of thyroid hormones. We investigated whether TSH has any effects on glucose tolerance and insulin sensitivity in the skeletal muscle using diet-induced obesity (DIO) mouse models and rodent skeletal muscle cells. TSH improved glucose tolerance in DIO mice and this was associated with an improvement of skeletal muscle insulin sensitivity resulting from the increased expression of insulin receptor substrate (IRS)-1 protein and mRNA therein. TSH significantly increased both basal and insulin-stimulated glucose transport in rat L6 myotubes and increased the expression of IRS-1 protein and mRNA in these cells as well. TSH also stimulated Irs1 promoter activation; this stimulation was abolished by protein kinase A (PKA) inhibition using H89 or by mutation of the cAMP-response element site located at -1155 to -875 bp of the Irs1 promoter region, supporting a novel role of TSH activated-cAMP/PKA/CREB signaling in the regulation of Irs1 expression. In conclusion, TSH improves insulin sensitivity in skeletal muscle by increasing Irs1 gene expression. This regulatory effect is mediated by a PKA-CREB-dependent pathway.

Application of whole-body FDG-PET for cancer screening in a cohort of hospital employees

Whole-body positron emission tomography/computed tomography with the glucose analog 2-[F]fluoro-2-deoxy-D-glucose (FDG-PET/CT) has been extensively used to screen for underlying malignancies in asymptomatic individuals. We were able to survey a cohort of hospital employees using FDG-PET/CT and to report the results herein.A total of 116 hospital employees older than 55 years old were offered whole-body FDG-PET in our hospital. Ninety-seven employees (83.6%) completed the assessment from February 2014 to August 2014 in our PET center. The final confirmation of cancer was based on pathologic examination and follow-up after more than 1 year.Among the 97 participants, 92 were asymptomatic and 5 presented with previously diagnosed cancers. Six of the 92 asymptomatic participants (6.6%) with significant nodular lesions were referred for histological or cytological evaluation of the possibility of malignancy, and 1 case was considered clinically important and required surgical resection. The cancer discovery rate was 3.3% (3/92) with positive predictive value of 50% (3/6). In the 5 participants with previously identified cancers, no recurrence or metastasis was detected.The offer of whole-body FDG-PET for cancer screening was welcomed with enthusiasm by most of the hospital employees. PET/CT combines the merits of PET and CT and can be administered to and provide benefits to a select group of hospital employees.

Application of molecular biology of differentiated thyroid cancer for clinical prognostication

Although cancer outcome results from the interplay between genetics and environment, researchers are making a great effort for applying molecular biology in the prognostication of differentiated thyroid cancer (DTC). Nevertheless, role of molecular characterisation in the prognostic setting of DTC is still nebulous. Among the most common and well-characterised genetic alterations related to DTC, including mutations of BRAF and RAS and RET rearrangements, BRAF^V600E is the only mutation showing unequivocal association with clinical outcome. Unfortunately, its accuracy is strongly limited by low specificity. Recently, the introduction of next-generation sequencing techniques led to the identification of TERT promoter and TP53 mutations in DTC. These genetic abnormalities may identify a small subgroup of tumours with highly aggressive behaviour, thus improving specificity of molecular prognostication. Although knowledge of prognostic significance of TP53 mutations is still anecdotal, mutations of the TERT promoter have showed clear association with clinical outcome. Nevertheless, this genetic marker needs to be analysed according to a multigenetic model, as its prognostic effect becomes negligible when present in isolation. Given that any genetic alteration has demonstrated, taken alone, enough specificity, the co-occurrence of driving mutations is emerging as an independent genetic signature of aggressiveness, with possible future application in clinical practice. DTC prognostication may be empowered in the near future by non-tissue molecular prognosticators, including circulating BRAF^V600E and miRNAs. Although promising, use of these markers needs to be refined by the technical sight, and the actual prognostic value is still yet to be validated.

Targeted treatments of radio-iodine refractory differentiated thyroid cancer

Radio-iodine refractory metastatic thyroid cancers are rare and their management was until recently relatively complex. New therapeutic agents, kinase inhibitors, joined since the early 2000s the fight against these cancers with very promising results. These targeted agents showed for two of them (sorafenib; lenvatinib), in randomized phase III trials, a significant improvement in response rate and progressionfree survival when compared to placebo, leading to the first approval for radio-iodine refractory metastatic thyroid cancers. In parallel, patients also benefited from the development of interventional radiology techniques and organization of cares in oncology, with multidisciplinary management strengthened by the creation of a national network (TUTHYREF).

PI3K/AKT Pathway and Its Mediators in Thyroid Carcinomas

Thyroid malignancies are the most common endocrine system carcinomas, with four histopathological forms. The phosphoinositide 3-kinase-protein kinase B/AKT (PI3K-PKB/AKT) pathway is one of the most critical molecular signaling pathways implicated in key cellular processes. Its continuous activation by several aberrant receptor tyrosine kinases (RTKs) and genetic mutations in its downstream effectors result in high cell proliferation in a broad number of cancers, including thyroid carcinomas. In this review article, the role of different signaling pathways of PI3K/AKT in thyroid cancers, with the emphasis on the PI3K/AKT/mammalian target of rapamycin (mTOR), PI3K/AKT/forkhead box O (FOXO) and PI3K/AKT/phosphatase and tensin homolog deleted on chromosome ten (PTEN) pathways, and various therapeutic strategies targeting these pathways have been summarized. In most of the in vitro studies, agents inhibiting mTOR in monotherapy or in combination with chemotherapy for thyroid malignancies have been introduced as promising anticancer therapies. FOXOs and PTEN are two outstanding downstream targets of the PI3K/AKT pathway. At the present time, no study has been undertaken to consider thyroid cancer treatment via FOXOs and PTEN targeting. According to the critical role of these proteins in cell cycle arrest, it seems that a treatment strategy based on the combination of FOXOs or PTEN activity induction with PI3K/AKT downstream mediators (e.g., mTOR) inhibition will be beneficial and promising in thyroid cancer treatment.

miR-148a inhibits self-renewal of thyroid cancer stem cells via repressing INO80 expression

Anaplastic thyroid carcinoma (ATC) is aggressive and lethal with extrathyroidal invasion, distant metastasis, and resistance to conventional therapies. Cancer stem cells (CSCs) are proposed to be responsible for high recurrence rate in ATC. MicroRNAs (miRNAs) have recently been found as an important class of cellular regulators of ATC carcinogenesis. Identification of CSC-related miRNAs and targets is therefore a priority for the development of new therapeutic paradigms. Patient-derived ATC cells were cultured in conditional media on poly-hema-treated dish. ATC CSCs were isolated and enriched through as a series of steps including initial isolation of sphere-forming CSC population, subsequent amplification of this CSC population in a xenograft model treated with cisplatin, and purification of CSCs from xenograft tumors followed by final enrichment using sphere-forming assays. Expression of CSC markers was measured by flow cytometry, immunofluorescence staining, qPCR and western blot analyses. Expression of miRNAs in ATC-CSCs was profiled by microarray analysis. Proliferation and differentiation rates were determined based on the size of spheres formed in vitro and tumors formed in vivo. We successfully isolated and enriched an ATC-CSC population. We identified 17 miRNAs differentially expressed in primary ATC cells vs. ATC-CSCs, among which miRNA-148a was significantly downregulated in ATC-CSCs. Overexpression of miRNA148a in ATC-CSCs induced cell cycle arrest and loss of stem cell characteristics. In addition, we identified INO80 as a target gene of miR-148a. The expression of INO80 was upregulated in ATC-CSCs and downregulated upon miRNA-148 overexpression. Overexpression of miRNA-148a and knockdown of INO80 acted synergistically to decrease the expression of stem cell marker genes as well as to attenuate stem cell-specific properties including the ability to form tumors. This study identified novel contrasting roles for miR-148a and INO80 in the regulation of the stemness of ATC-CSCs and their capacity to initiate tumor formation. Our findings may open a new avenue for therapeutic development against ATC that targets INO80 in the CSCs through enhancing miRNA-148a levels.

Overexpression of NDRG2 Increases Iodine Uptake and Inhibits Thyroid Carcinoma Cell Growth In Situ and In Vivo

Medullary thyroid carcinoma (MTC) is an uncommon and highly aggressive tumor of the neuroendocrine system, which derives from the neuroendocrine C cells of the thyroid gland. Except for surgical resection, there are not very many effective systemic treatment options for MTC. N-Myc downstream-regulated gene 2 (NDRG2) had a significantly lower expression in MTC compared with normal thyroid tissue. However, the function of NDRG2 in MTC oncogenesis is largely unknown. In this study, we found that overexpression of NDRG2 inhibited the proliferation of TT cells (human medullary thyroid carcinoma cells) in vitro and suppressed the development of MTC in a nude mouse xenograft model. Further analysis revealed that NDRG2 arrested the cell cycle G₀/G₁ phase progression and induced TT cell apoptosis. Moreover, NDRG2 overexpression may mediate the antiproliferative effect by reducing cyclin D1 and cyclin E protein levels. We also found aberrant NDRG2-mitigated TT cell migration and invasion in vitro. Sodium/iodide symporter (NIS) mediates active I⁻ transport into the thyroid follicular cells, and radionuclide treatment is a promising therapy for MTC. Our current data revealed that NDRG2 overexpression enhanced NIS level in TT cells and increased their iodine uptake in vitro. Furthermore, ^99mTcO₄⁻ radionuclide imaging of the xenograft tumors indicated that NDRG2 could promote NIS-mediated radionuclide transport. In conclusion, the present study suggested that NDRG2 is a critical molecule in the regulation of MTC biological behavior and a potential promoter in radioactive iodine therapy.

Silencing of hypoxia-inducible factor-1α promotes thyroid cancer cell apoptosis and inhibits invasion by downregulating WWP2, WWP9, VEGF and VEGFR2

Adaptation to hypoxia is an important process physiologically and pathologically. Hypoxia-inducible factor-1α (HIF-1α) participates in the cancer biology of numerous endocrine tumors, including their proliferation and differentiation. In the present study, the hypothesis that HIF-1α promotes tumorigenesis in thyroid cancer via upregulating angiogenesis-associated markers is investigated. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were used to examine the expression of HIF-1α in thyroid cancer cell lines, and to detect the expression of WW domain containing E3 ubiquitin protein ligase (WWP)2, WWP9, vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2) in MZ-CRC-1 and TT thyroid cancer cells. Cell proliferation was measured using a Cell Count Kit-8. Cell apoptosis and cell cycle was assessed by flow cytometry. Cell invasive ability was examined by Matrigel transwell analysis. RT-qPCR and western blot analyses demonstrated that the mRNA and protein expression levels of HIF-1α were significant higher in MZ-CRC-1 and TT thyroid cancer cells than in another three thyroid cancer cells (P<0.01). HIF-1α knockdown cells demonstrated inhibition of cell proliferation and invasion, arrested cell cycle at the G1 phase, and induction of cell apoptosis. The protein expression levels of WWP2, WWP9, VEGF and VEGFR2 were decreased in HIF-1α knockdown MZ-CRC-1 and TT cells. In conclusion, HIF-1α may be important in cell apoptosis and invasion of thyroid cancer cells, likely through regulating WWP2, WWP9, VEGF and VEGFR2 expression.

Progress in Endocrine Neoplasia

Most endocrine tumors are benign, and afflicted patients usually seek medical advice because of symptoms caused by too much, or too little, native hormone secretion or the impingement of their tumor on a vital structure. Malignant endocrine tumors represent a more serious problem, and patient cure often depends on early diagnosis and treatment. The recent development of novel molecular therapeutics holds great promise for the treatment of patients with locally advanced or metastatic endocrine cancer. In this CCR Focus, expert clinical investigators describe the molecular characteristics of various endocrine tumors and discuss the current status of diagnosis and treatment. Clin Cancer Res; 22(20); 4981-8. ©2016 AACR See all articles in this CCR Focus section, "Endocrine Cancers Revising Paradigms".

MicroRNAs in the thyroid

MicroRNAs (miRNAs) are small non-coding RNA comprising approximately 19-25 nucleotides. miRNAs can act as tumour suppressors or oncogenes, and aberrant expression of miRNAs has been reported in several human cancers and has been associated with cancer initiation and progression. Recent evidence suggests that miRNAs play a major role in thyroid carcinogenesis. In this review, we summarize the role of miRNAs in thyroid cancer and describe the oncogenic or tumour suppressor function of miRNAs as well as their clinical utility as prognostic or diagnostic markers in thyroid cancer.

Overexpression of Interleukin-4 in the Thyroid of Transgenic Mice Upregulates the Expression of Duox1 and the Anion Transporter Pendrin

BACKGROUND

The dual oxidases (Duox) are involved in hydrogen peroxide generation, which is essential for thyroid hormone synthesis, and therefore they are markers of thyroid function. During inflammation, cytokines upregulate DUOX gene expression in the airway and the intestine, suggesting a role for these proteins in innate immunity. It was previously demonstrated that interleukin-4 (IL-4) upregulates DUOX gene expression in thyrocytes. Although the role of IL-4 in autoimmune thyroid diseases has been studied extensively, the effects of IL-4 on thyroid physiology remain largely unknown. Therefore, a new animal model was generated to study the impact of IL-4 on thyroid function.

METHODS

Transgenic (Thyr-IL-4) mice with thyroid-targeted expression of murine IL-4 were generated. Transgene expression was verified at the mRNA and protein level in thyroid tissues and primary cultures. The phenotype of the Thyr-IL-4 animals was characterized by measuring serum thyroxine (T4) and thyrotropin levels and performing thyroid morphometric analysis, immunohistochemistry, whole transcriptome sequencing, quantitative reverse transcription polymerase chain reaction, and ex vivo thyroid function assays.

RESULTS

Thyrocytes from two Thyr-IL-4 mouse lines (#30 and #52) expressed IL-4, which was secreted into the extracellular space. Although 10-month-old transgenic animals had T4 and thyrotropin serum levels in the normal range, they had altered thyroid follicular structure with enlarged follicles composed of elongated thyrocytes containing numerous endocytic vesicles. These follicles were positive for T4 staining the colloid, indicating their capacity to produce thyroid hormones. RNA profiling of Thyr-IL-4 thyroid samples revealed modulation of multiple genes involved in inflammation, while no major leukocyte infiltration could be detected. Upregulated expression of Duox1, Duoxa1, and the pendrin anion exchanger gene (Slc26a4) was detected. In contrast, the iodide symporter gene Slc5a5 was markedly downregulated resulting in impaired iodide uptake and reduced thyroid hormone levels in transgenic thyroid tissue. Hydrogen peroxide production was increased in Thyr-IL-4 thyroid tissue compared with wild-type animals, but no significant oxidative stress could be detected.

CONCLUSIONS

This is the first study to show that ectopic expression of IL-4 in thyroid tissue upregulates Duox1/Duoxa1 and Slc26a4 expression in the thyroid. The present data demonstrate that IL-4 could affect thyroid morphology and function, mainly by downregulating Slc5a5 expression, while maintaining a normal euthyroid phenotype.

Molecular Testing of Thyroid Nodules: A Review of Current Available Tests for Fine-Needle Aspiration Specimens

Context.—

Fine-needle aspiration of thyroid nodules is a reliable diagnostic method to determine the nature of thyroid nodules. Nonetheless, indeterminate cytology diagnoses remain a diagnostic challenge. The development of multiplex molecular techniques and the identification of genetic alterations associated with different follicular cell–derived cancers in the thyroid have led to the introduction of several commercially available tests.

Objective.—

To summarize the most common commercially available molecular testing in thyroid cancer, focusing on the technical features and test performance validation.

Data Sources.—

Peer-reviewed original articles, review articles, and published conference abstracts were reviewed to analyze the advantages and limitations of the most common tests used in the evaluation of thyroid needle aspirations.

Conclusions.—

The most common tests available include the Afirma Gene Expression Classifier, ThyGenX, and ThyroSeq. The excellent negative predictive value (NPV) of the Afirma test allows it to be used as a “rule out” test. ThyGenX analyzes a panel of DNA mutations and RNA translocation fusion markers to assess the risk of malignancy with good NPV and positive predictive value. ThyroSeq is a next-generation sequencing–based gene mutation and fusion test that has been reported to have the best NPV and positive predictive value combined, suggesting that it can be used as a “rule in” and “rule out” test. Molecular testing of cytology specimens from thyroid nodules has the potential to play a major role in the evaluation of indeterminate thyroid lesions.

Shifting patterns of genomic variation in the somatic evolution of papillary thyroid carcinoma

Background

Cancer is increasingly understood to arise in the context of dynamically evolving genomes with continuously generated variants subject to selective pressures. Diverse mutations have been identified in papillary thyroid carcinoma (PTC), but unifying theories underlying genomic change are lacking. Applying a framework of somatic evolution, we sought to broaden understanding of the PTC genome through identification of global trends that help explain risk of tumorigenesis.

Methods

Exome sequencing was performed on 53 PTC and matched adjacent non-tumor thyroid tissues (ANT). Single nucleotide substitution (SNS) signatures from each sample pair were divided into three subsets based on their presence in tumor, non-tumor thyroid, or both. Nine matched blood samples were sequenced and SNS signatures intersected with these three subsets. The intersected genomic signatures were used to define branch-points in the evolution of the tumor genome, distinguishing variants present in the tissues’ common ancestor cells from those unique to each tissue type and therefore acquired after genomic divergence of the tumor, non-tumor, and blood samples.

Results

Single nucleotide substitutions shared by the tumor and the non-tumor thyroid were dominated by C-to-T transitions, whereas those unique to either tissue type were enriched for C-to-A transversions encoding non-synonymous, predicted-deleterious variants. On average, SNSs of matched blood samples were 81 % identical to those shared by tumor and non-tumor thyroid, but only 12.5 % identical to those unique to either tissue. Older age and BRAF mutation were associated with increased SNS burden.

Conclusions

The current study demonstrates novel patterns of genomic change in PTC, supporting a theory of somatic evolution in which the zygote’s germline genome undergoes continuous remodeling to produce progressively differentiated, tissue-specific signatures. Late somatic events in thyroid tissue demonstrate shifted mutational spectra compared to earlier polymorphisms. These late events are enriched for predicted-deleterious variants, suggesting a mechanism of genomic instability in PTC tumorigenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2665-7) contains supplementary material, which is available to authorized users.

UHRF1 suppression promotes cell differentiation and reduces inflammatory reaction in anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC), an undifferentiated subtype of thyroid cancer, is one of the most malignant endocrine cancer with low survival rate, and resistant to chemotherapy and radiation therapy. Here we found that UHRF1 was highly expressed in human ATC compared with normal tissue and papillary thyroid cancer (PTC). Knockdown of UHRF1 inhibited proliferation of ATC in vitro and in vivo. Consistently, overexpression of UHRF1 promoted the proliferation of thyroid cancer cells. Moreover, UHRF1 suppression induced differentiation of three-dimensional (3D) cultured ATC cells and down-regulated the expression of dedifferentiation marker (CD97). The stem cell markers (Sox2, Oct4 and Nanog) were suppressed simultaneously. In addition, UHRF1 knockdown reduced the transcription of cytokines (IL-8, TGF-α and TNF-α), which might relieve the inflammatory reaction in ATC patients. This study demonstrated a role of UHRF1 in ATC proliferation, dedifferentiation and inflammatory reaction, presenting UHRF1 as a potential target in ATC therapy.

Quantitative assessment of preoperative serum thyrotropin level and thyroid cancer

Thyroid stimulating hormone (TSH) is the major growth factor for thyrocytes, but the pathogenic role of serum TSH in thyroid cancer (TC) is unknown. The association between TSH level and the development of thyroid cancer has been widely evaluated recently. However, the results remain conflicting. To develop an understanding of the relationship between TSH exposure and thyroid cancer, a meta-analysis of 56 studies involving 20227 thyroid cancer cases and 50003 controls with benign thyroid nodule was performed. Overall, significantly increased TSH level was observed in thyroid cancer patients compared with controls (RoM: 1.44, 95% CI: 1.32-1.56, P < 10-5). The pooled analyses also revealed that higher serum TSH level were significantly associated with the size of TC nodule and malignancy as well as lymph node metastasis. Furthermore, significantly increased THS levels were observed preferentially for papillary thyroid cancer when stratified by histological type of tumors. However, the diagnostic value of TSH level for TC might be limited. These results suggest that higher serum TSH concentration is associated with an increased risk of thyroid cancer.

Resistance of papillary thyroid cancer stem cells to chemotherapy

Thyroid carcinoma is the most common endocrine neoplasm, with the highest mortality rate of all the endocrine cancers. Among the endocrine malignancies, ~80% are papillary thyroid carcinomas (PTCs). In the initiation and progression of this tumor, genetic alterations in the mitogen-associated protein kinase pathway, including RAS point mutations, RET/PTC oncogene rearrangements and BRAF point mutations, play an important role, particularly in deciding targeted therapy. In the present study, a small population of thyroid tumor cells, known as tumor spheres, were isolated and characterized from PTC surgical samples. These spheres can be expanded indefinitely in vitro and give rise to differentiated adherent cells when cultivated in differentiative conditions. The present study showed by reverse transcription-polymerase chain reaction and flow cytometric analysis that the undifferentiated PTC cells exhibited a characteristic antigen expression profile of adult progenitor/stem cells. The cells were more resistant to chemotherapeutics, including bortezomib, taxol, cisplatin, etoposide, doxorubicin and vincristine, than differentiated PTC cells and the majority possessed a quiescent status, as revealed by the various cell cycle characteristics and anti-apoptotic protein expression. Such advances in cancer thyroid stem cell biology may provide relevant information for future targeted therapies.

Value of Molecular Tests in Cytologically Indeterminate Lesions of Thyroid

CONTEXT

Fine-needle aspiration has been the initial step in the workup of thyroid nodular lesions and has successfully reduced the number of unnecessary surgeries and improved preoperative malignancy detection. However, up to one-third of cases fall in the diagnostically "indeterminate group," which poses a patient-management challenge. objective: To review the characteristics of molecular tests useful for stratifying the malignancy risk of indeterminate thyroid lesions, including their advantages and limitations.

DATA SOURCES

PubMed.

CONCLUSIONS

Molecular tests are useful for triage of indeterminate thyroid nodules initially diagnosed by using fine-needle aspiration. Immunocytochemistry is readily available with the shortest turnaround time among the molecular tests but suffers from poor reproducibility and low interpretation concordance. Gene mutation analysis is superior in detecting malignancies as a rule-in test, despite low specificity. Next-generation sequencing seems promising but needs more validations before widespread use. Gene expression profiling is more suitable for detecting benign lesions as a rule-out test to avoid unnecessary surgeries but is not reliable in excluding malignancies. MicroRNA profiling has great potential for both risk stratification and predicting prognosis but is limited by significant variations in sensitivity and specificity. Although many questions still need to be answered, taken together, molecular tests are a promising option for classifying cytologically indeterminate thyroid nodular lesions.

Molecular genetics of thyroid cancer

The pathogenesis of the development and progression of thyroid cancer (TC) is far from being clear at present. Accumulated evidence suggests that it is a complex polygenic disorder for which genetic factors play an important role in disease aetiology. Here we review the literature to report the genetic variations and alterations that have been described in the aetiology of TC. The functional effects of some mutations and single nucleotide polymorphisms on TC are validated, establishing the role of sequence variations in this cancer. However, large prospective studies are still required to evaluate the diagnostic and prognostic value of these genetic determinants in clinical practice.

Clinical Manifestations and Gene Expression in Patients with Conventional Papillary Thyroid Carcinoma Carrying the BRAF(V600E) Mutation and BRAF Pseudogene

BACKGROUND

The association of BRAF(V600E) with the clinical manifestations of papillary thyroid carcinoma (PTC) remains controversial. Recent studies have shown that the BRAF pseudogene can activate the MAPK pathway and induce tumorigenesis. This study investigated the association of BRAF(V600E), the BRAF pseudogene, and their mRNA levels with clinical features and thyroid-specific gene expression in conventional PTCs.

MATERIALS AND METHODS

A total of 78 specimens were collected from patients with conventional PTCs. RNA was isolated, and quantitative polymerase chain reaction was used to measure the mRNA levels of BRAF, the BRAF pseudogene, and thyroid-specific and tumor-related genes. Immunohistochemical (IHC) staining of BRAF, ERK, sodium-iodide symporter (NIS), thyrotropin receptor, glucose transporter 1, and Ki67 was also performed.

RESULTS

BRAF(V600E) and the BRAF pseudogene were detected in 73.0% (57/78) and 91.7% (44/48), respectively, of the conventional PTCs. The presence of BRAF(V600E) was not associated with the multiple clinical features assessed or the recurrence rate during 76.9 ± 47.2 months of follow-up. Neither was it associated with IHC staining or tumor-related/thyroid-specific gene expression, except for decreased NIS gene expression. The BRAF pseudogene was not associated with clinical characteristics or thyroid-specific gene expression, except for decreased decoy receptor 3 (DCR3) expression. High BRAF mRNA levels were associated with bilateral and multifocal lesions, and BRAF-pseudogene mRNA levels were positively correlated with BRAF mRNA levels (r = 0.415, p = 0.009).

CONCLUSION

These results do not support the use of the BRAF(V600E) mutation as a prognostic marker of conventional PTC. However, the association of high BRAF mRNA levels with more advanced clinical features suggests that BRAF mRNA levels might be a more useful clinical marker of PTCs, independent of the BRAF(V600E) mutation status. The correlation between BRAF-pseudogene mRNA levels and BRAF mRNA levels in PTCs is in agreement with the hypothesis that the BRAF pseudogene regulates BRAF expression during tumorigenesis by acting as competitive noncoding RNA. However, additional studies with larger sample sizes are required to confirm these findings.

PATZ1 is a target of miR-29b that is induced by Ha-Ras oncogene in rat thyroid cells

The regulatory transcriptional factor PATZ1 is constantly downregulated in human thyroid cancer where it acts as a tumour suppressor by targeting p53-dependent genes involved in Epithelial-Mesenchymal Transition and cell migration. The aim of the present work was to elucidate the upstream signalling mechanisms regulating PATZ1 expression in thyroid cancer cells. The bioinformatics search for microRNAs able to potentially target PATZ1 led to the identification of several miRNAs. Among them we focused on the miR-29b since it was found upregulated in rat thyroid differentiated cells transformed by the Ha-Ras oncogene towards a high proliferating and high migratory phenotype resembling that of anaplastic carcinomas. Functional assays confirmed PATZ1 as a target of miR-29b, and, consistently, an inverse correlation between miR-29b and PATZ1 protein levels was found upon induction of Ha-Ras oncogene expression in these cells. Interestingly, restoration of PATZ1 expression in rat thyroid cells stably expressing the Ha-Ras oncogene decreased cell proliferation and migration, indicating a key role of PATZ1 in Ras-driven thyroid transformation. Together, these results suggest a novel mechanism regulating PATZ1 expression based on the upregulation of miR-29b expression induced by Ras oncogene.

Roles of SHARP1 in thyroid cancer

SHARP1 is a basic helix‑loop‑helix transcription factor involved in various cellular processes, including proliferation and differentiation. The present study assessed the role of SHARP1 in the progression and invasion of thyroid cancer. PCR and western blot analysis demonstrated that in thyroid cancer tissues, SHARP1 was significantly downregulated at the mRNA and protein level compared with that in normal tissues. Furthermore, SHARP1 was downregulated in the TT and TPC‑1 thyroid cancer cell lines compared with a normal thyroid cell line, while it was upregulated in other thyroid cancer cell lines. Overexpression of SHARP1 in TT and TPC‑1 cells significantly inhibited the cell viability, migration and invasion in vitro. Furthermore, the protein and mRNA levels of HIF‑1α were found to be decreased in TT and TPC‑1 cells following forced overexpression of SHARP1. In addition, silencing of HIF‑1α reduced the viability, migration and invasion of TT and TPC-1 cells. In conclusion, the present study indicated that SHARP1 acts as a tumor suppressor in thyroid cancer and that its downregulation may contribute to the proliferation, migration and invasion of thyroid cancer cells through mechanisms possibly involving HIF‑1α, suggesting that SHARP1 may be an important therapeutic target for the treatment of thyroid cancer.

Mechanisms and kinetics of proliferation and fibrosis development in a mouse model of thyrocyte hyperplasia

IFN-γ(-/-) NOD.H-2h4 mice develop autoimmune disease with extensive hyperplasia and proliferation of thyroid epithelial cells (TEC H/P) and fibrosis. Splenic T cells from donors with severe TEC H/P transfer TEC H/P to SCID recipients. The goal of this study was to determine what factors control TEC H/P development/progression by examining T cells, markers of apoptosis, senescence and proliferation in thyroids of SCID recipients over time. At 28days, T cell infiltration was maximal, thyrocytes were proliferating, and fibrosis was moderate. At days 60 and 90, thyroids were larger with more fibrosis. T cells, cytokines and thyrocyte proliferation decreased, and cell cycle inhibitor proteins, and anti-apoptotic molecules increased. T cells and thyrocytes had foci of phosphorylated histone protein H2A.X, indicative of cellular senescence, when TEC H/P progressed and thyrocyte proliferation declined. Some thyrocytes were regenerating at day 90, with irregularly shaped empty follicles and ciliated epithelium. Proliferating thyrocytes were thyroid transcription factor (TTF1)-positive, suggesting they derived from epithelial cells and not brachial cleft remnants.

The "next-generation" knowledge of papillary thyroid carcinoma

The application of Next-Generation Sequencing for studying the genetics of papillary thyroid carcinomas (PTC) has recently revealed new somatic mutations and gene fusions as potential new tumor-initiating events in patients without any known driver lesion. Gene and miRNA expression analyses defined clinically relevant subclasses correlated to tumor progression. In addition, it has been shown that tumor driver mutations in BRAF, and RET rearrangements - altogether termed "BRAF-like" carcinomas - have a very similar expression pattern and constitute a distinct category. Conversely, "RAS-like" carcinomas have a different genomic, epigenomic, and proteomic profile. These findings justify the need to reconsider PTC classification schemes.

The BH3 mimetic drug ABT-737 induces apoptosis and acts synergistically with chemotherapeutic drugs in thyroid carcinoma cells

BACKGROUND

Patients with dedifferentiated and anaplastic thyroid carcinomas that do not take up radioiodine are resistant to chemotherapeutic treatment and external irradiation and thus are difficult to treat. Direct induction of apoptosis is a promising approach in these apoptosis-resistant tumor cells. The BH3 mimetic ABT-737 belongs to a new class of drugs that target anti-apoptotic proteins of the BCL-2 family and facilitate cell death. The purpose of this study was to investigate the effect of ABT-737 alone or in combination with chemotherapeutic drugs on thyroid carcinoma cell lines.

METHODS

A total of 16 cell lines derived from follicular, papillary, and anaplastic thyroid carcinomas were treated with ABT-737. Cell viability was measured with MTT assay. Cell death was determined by cell cycle phase distribution and subG1 peak analyses, determination of caspase 3/7 activity and caspase cleavage products, lactate dehydrogenase (LDH) liberation assays and LC3 analysis by western blot.

RESULTS

The number of viable cells was decreased in all cell lines examined after ABT-737 treatment, with IC50 values ranging from 0.73 to 15.6 μM. Biochemical markers of apoptosis like caspase activities, caspase cleavage products and DNA fragmentation determined as SubG1 peak were elevated after ABT-737 treatment, but no LC3 cleavage was induced by ABT-737 indicating no autophagic processes. In combination with doxorubicin and gemcitabine, ABT-737 showed synergistic effects on cell viability.

CONCLUSIONS

With these experiments we demonstrated the efficacy of the BH3 mimetic drug ABT-737 against dedifferentiated thyroid carcinoma cells of various histological origins and showed synergistic effects with chemotherapeutic drugs. ABT-737-treated cells underwent an apoptotic cell death. ABT-737 and related BH3 mimetic drugs, alone or in combination, may thus be of value as a new therapeutic option for dedifferentiated thyroid carcinomas.

High-Frequency Ultrasound-Guided Injection for the Generation of a Novel Orthotopic Mouse Model of Human Thyroid Carcinoma

BACKGROUND

Thyroid carcinoma is the most common endocrine malignancy and has an increasing incidence. High-frequency ultrasound (HFUS) has a spatial resolution of 30 μm, which is a property that has been exploited for thyroid visualization and analysis in mice. The aim of this study was to generate a novel orthotopic mouse model of human follicular thyroid carcinoma (FTC) using an HFUS-guided injection system.

METHODS

Twenty Balb/C nude mice were injected in the right lobe of the thyroid with 2 × 10(6) FTC-133 cells using the microinjection HFUS-guided system, and 20 mice, used as a control, underwent surgical orthotopic implantation of 2 × 10(6) FTC-133 cells in the right lobe of the thyroid. All mice underwent HFUS imaging two weeks after cell injection; HFUS examinations and tumor volume (TV) measurements were repeated weekly. Micro-computed tomography was performed at different time points to determine whether lung metastasis had occurred. TVs were compared between the two models (surgical vs. HFUS-guided) using the Mann-Whitney U-test, and the Mantel-Cox log-rank test was applied to evaluate the death hazard. Hematoxylin and eosin analysis of formalin-fixed, paraffin-embedded mouse tissue was performed to validate the in vivo imaging results.

RESULTS

Of the HFUS-guided injected mice, 9/18 survived up to 40 days after the injection of tumor cells. Mice injected surgically had 100% mortality at day 29. Of 38 mice, 29 (14/18 HFUS, 15/20 surgical) showed metastasis in the salivary glands and lymph nodes, and 13 (10/18 HFUS, 3/20 surgical) also showed metastasis in the lungs, which was confirmed by histological analysis. In the surgical group, there was an evident, frequent (12/20 mice) involvement of the contralateral lobe of the thyroid, whereas this feature was only detected in 1/18 mice in the HFUS group. Statistical analysis showed the same pattern of growth in the two groups, and a significant hazard in the mice in the surgical group (p = 0.03).

CONCLUSIONS

This study demonstrated the technical feasibility of an HFUS-guided orthotopic mouse model of FTC. The HFUS-guided orthotopic model is easily reproducible and allows prolonged monitoring of the disease because the animals showed an increased survival rate.

Proteomics of thyroid tumours provides new insights into their molecular composition and changes associated with malignancy

Around 5% of the general population have palpable thyroid nodules. Although most thyroid tumours are benign, thyroid cancer represents the most common malignancy of the endocrine system, comprising mainly follicular and papillary thyroid carcinomas. Previous studies have shed some light on the molecular pathogenesis of thyroid cancer but there have not been any comprehensive mass spectrometry-based proteomic studies of large scale to reveal protein expression differences between thyroid tumours and the molecular alterations associated with tumour malignancy. We applied data-independent acquisition mass spectrometry which enabled quantitative expression analysis of over 1,600 proteins from 32 specimens to compare normal thyroid tissue with the three most common tumours of the thyroid gland: follicular adenoma, follicular carcinoma and papillary carcinoma. In follicular tumours, we found marked reduction of the tumour suppressor and therapeutic target extracellular protein decorin. We made the novel observation that TGFβ-induced protein ig-h3 (TGFBI) was found frequently overexpressed in follicular carcinoma compared with follicular adenoma. Proteomic pathway analysis showed changes in papillary carcinoma were associated with disruption of cell contacts (loss of E-cadherin), actin cytoskeleton dynamics and loss of differentiation markers, all hallmarks of an invasive phenotype.